This invention relates to spacers for use in nuclear fuel bundles, the spacers maintaining individual fuel rods or tubes containing fissionable materials in their designed spaced apart relation. More particularly, a spacer is disclosed which has a spring that can be placed within and removed from the previously assembled spacer. Further, provision is made for the insertion of fuel rods through the spacers of a fuel bundle with the spring of the spacer in the compressed, partially inserted state for avoiding scratching of inserted fuel rods on fuel bundle assembly.